1. Field of the Invention
The present invention relates to a wet type flue gas desulfurization apparatus that can desulfurize flue gas by causing the flue gas to come into gas-liquid contact with an absorbent.
2. Description of the Related Art
Flue gas generated in large combustion facilities, such as a plant or the like, includes SOX (sulfur oxide), such as sulfur dioxide (SO2). Accordingly, it is desired to remove sulfur oxides from (i.e., to desulfurize) flue gas. In order to desulfurize flue gas, a wet type flue gas desulfurization apparatus has been widely used, and this wet type flue gas desulfurization apparatus desulfurizes flue gas by using an absorbent that includes an alkaline material, such as alkaline metal (this type of flue gas desulfurization apparatus will hereafter be simply referred to as a “FGD apparatus”). A FGD apparatus employs a limestone gypsum method, a magnesium hydroxide method, a sodium hydroxide method, an ammonia absorption method, or the like. In particular, the limestone gypsum method is used in very many FGD apparatuses. In many cases, when the limestone gypsum method is employed, limestone slurry which is produced by suspending a limestone (CaCO3 (calcium carbonate)) in water, is used as an absorbent. In general, in a FGD apparatus, flue gas is desulfurized by coming into gas-liquid contact with the absorbent that has been sprayed from nozzles inside an absorption tower. Furthermore, the absorbent contacted in the desulfurization process is circulated within the FGD apparatus, and therefore, is repeatedly contacted within the FGD apparatus.
However, in many cases, the absorbent flowing in a circulation path may contain: scales, such as calcium sulfite (CaSO3) or calcium sulfate (CaSO4) or the like, which may be generated in the desulfurization process; and impurities which may intrude from outside. The scales and the impurities (hereinafter collectively referred to as “scales etc.”) may cause clogging in nozzles and the circulation path. The absorbent may not be appropriately sprayed from the nozzles due to the clogging so that the desulfurization efficiency may degrade. As a result, the FGD apparatus cannot be stably operated. In order to solve the above-described problem, a related FGD apparatus is provided with a mesh for collecting the scales etc., and the mesh is arranged in the absorbent circulation path. In addition, in a related FGD apparatus discussed in Japanese Utility Model Registration Publication No. 02-027870, a grinding mechanism for grinding scales and the like, is provided in the absorbent circulation path.